Visceral leishmaniasis in large Brazilian cities: challenges for control

A, Celestino A, Hospinal-Santiani M, de Souza A, Mychalizen M, Borges ME, Piechnik CA. One piece of the puzzle: Modeling vector presence and environment reveals seasonality, distribution, and prevalence of sandflies and Leishmania in an expansion area

The recent geographic spread of Leishmania infantum along the borders of Argentina, Brazil and Paraguay has been highlighted. In our previous study, Lutzomyia longipalpis was found in 55 of 123 patches surveyed, and in some patches, sandflies were found at higher densities, forming hotspots. Based on the One Health approach, we investigated the seasonality of the vector, the presence of parasite DNA, and the environmental factors that contribute to vector and parasite dispersal in these previously described hotspots in Foz do Iguaçu, Brazil. Entomological surveys were conducted monthly for one year. Fourteen hotspots peridomicile and six intradomicile were sampled. PCR was used to assess the prevalence of Leishmania DNA in sandflies. Zero-inflated negative binomial regression was used to determine the association of micro- and mesoscale environmental variables with the occurrence and abundance of the three most abundant sandfly species sampled. A total of 3543 species were captured, with Lutzomyia longipalpis being the predominant species (71.78%) of the 13 species found. Evandromyia edwardsi, Expapillata firmatoi, Micropygomyia ferreirana and Pintomyia christenseni were reported for the first time in the region. NDVI, distance to water, precipitation, west-to-east wind, wind speed, maximum and minimum relative humidity, and sex were significant variables associated with vector presence/abundance in the environment. Vector presence/abundance in the peridomicile was associated with precipitation, altitude, maximum temperature, minimum and maximum relative humidity, west-to-east wind, wind speed, and sex. Leishmania DNA was detected in an average of 21% of Lu. longipalpis throughout the year. Vector abundance is concentrated in urban and peri-urban areas, with some specimens present in different parts of the city and some sites with high vector abundance. This distribution suggests that the risk of actual contact between humans and parasite vectors in urban areas during the epidemic period is associated with patches of peri-urban vegetation and then extends into urban areas.

Control of Canine Visceral Leishmaniasis: A Success Case Based on Deltamethrin 4% Collars

The effect of employing collars impregnated with deltamethrin 4% (DM4) to control canine visceral leishmaniasis (CVL) was evaluated. as were the individual factors associated with this infection. A cohort study that included household dogs was conducted between 2002 and 2006. The presence of pathognomonic signals, peridomiciliary sleep habits and breed were the main factors associated with the infection. The use of DM4 collars contributed to the reduction of CVL with an effectiveness of 66%, and the dogs' survival rate was greater than 90% at 50 months. In conclusion, the adoption of DM4 collars reduced the number of euthanized canines and in the incidence of CVL, and this reduction was sustained for one year after discontinuing the use of the collar.

Validation of ELISA with recombinant antigens in serological diagnosis of canine Leishmania infantum infection

BACKGROUND

Dogs are the main peridomiciliary reservoir of Leishmania infantum thus the correct diagnosis of infection is essential for the control of the transmission and treatment as well. However, the diagnosis is based on serological assays that are not fully effective.

OBJECTIVE

We aimed to establish an effective serological assay for the diagnosis of L. infantum infected dogs using Leishmania-derived recombinant antigens.

METHODS

Leishmania derived rK39-, rK28-, rKR95-based enzyme-linked immunosorbent assay (ELISA) was standardized using symptomatic and asymptomatic L. infantum-infected dogs. Then 2,530 samples from inquiry in endemic areas for VL were evaluated and the results compared with recommended assays by the Brazilian Ministry of Health (MH algorithm). Further samples from a cohort of 30 dogs were searched.

FINDINGS

For rK39-, rK28- and rKR95-ELISA the sensitivity was around 97% and specificity 100%. The positivity of these three ELISA in the inquiry samples was 27-28%, around 10% higher than the assays currently in use. When cohort samples were searched, we observed likely false-negative results (> 65%) with supposedly negative samples that turned positive six months later with the assays in use (MH algorithm).

MAIN CONCLUSIONS

For the diagnosis of L. infantum-infected dogs, rK39-based ELISA showed better diagnostic performance than other assays in use in Brazil and worldwide.

Spatial analysis of canine leishmaniasis in an area of transmission of the semi-arid region of the State of Paraíba, Brazil

Visceral leishmaniasis is a widely distributed zoonosis and canine infection is an important indicator of risk for the occurrence of the disease in humans. The goal of this analysis was to study the spatial clustering of canine leishmaniasis (CL) in the municipality of Santa Luzia, state of Paraíba. For this, 749 samples of canine plasma were tested using three serological tests. The dog was considered positive if it reacted in two serological tests. The location of the residences was performed with a Global Positioning System receiver (GPS Garmin® eTrex 30), and used to perform georeferencing and spatial analysis. The prevalence of CL was 15.49% and it was observed that most cases of the urban area were concentrated in the Frei Damião neighborhood, on the outskirts of the city, where a high-risk cluster for the occurrence of the disease was formed (p = 0.02; RR = 2.48). No statistically significant cluster was observed in rural areas. CL is widely distributed in the municipality of Santa Luzia in a heterogeneous manner and with a tendency to urbanization. The areas identified with high prevalence and highest risk should be prioritized to maximize the efficiency of the Visceral Leishmaniasis Surveillance and Control Program and minimize the chance of new canine and human cases.

Differentials in the epidemiological profile of canine visceral leishmaniasis in the semi-arid region of Paraíba, Brazil

ABSTRACT: The objective of this study was to estimate the prevalence of canine visceral leishmaniasis (CVL) and to identify the differences in associated factors to its occurrence in urban area and countrysides in the municipality of Santa Luzia located in the semi-arid region of Paraíba. In the years 2015 and 2016, 779 blood samples from dogs were collected. The prevalence was determined by three serological techniques, ELISA-S7® Kit, DPP® Rapid Test and EIE-LVC® Kit, considering positive the samples that reacted in at least two assays. Associated factors were determined by univariate and multivariate analyzes of the guardians’ responses to the epidemiological questionnaire. The prevalence of anti-Leishmania infantum antibodies in the studied municipality was 15.00% (117/779), being higher in the urban area (15.20%) than in the countryside (13.60%). The neighborhood with the highest prevalence was Frei Damião with 26.40% (33/125), being considered a hotspot (OR 1.245, p=0.007). Other associated factors were the semi-domiciliary breeding (OR 1.798, p=0.025), in the urban area, and hunting dog (OR 18.505, p=0.016), contact with cattle (OR 17.298, p=0.022) and environment where the dog is raised (OR 4.802, p=0.024) in the countryside. In the municipality of Santa Luzia, the prevalence of canine visceral leishmaniasis is high and the disease is widely distributed. Epidemiological differences between urban area and the countryside could be observed demonstrating the need for more adequate control measures for each locality and proving the urbanization process.

Clinical, epidemiological and transmission cycle aspects of leishmaniasis urbanization in Barreiras, Bahia, Brazil

Leishmaniasis remains one of the world's leading infectious diseases and a public health problem for Bahia and Brazil. We made a retrospective cohort study of leishmaniasis cases reported between 2007 and 2016 in the Barreiras city, an important agribusiness city whose urbanization process was recent. Leishmaniasis presented epidemiological data with similar characteristics of the disease in other regions of the Brazil, that is, with the highest prevalence of visceral leishmaniasis found in children, while cutaneous leishmaniais was found in adults. The disease presented an urban configuration with wide distribution in the Barreiras city. We found the vectors of the different clinical forms of the disease occurring in the urban area of Barreiras city, particularly the sand fly of the Lutzmyia longipalpis, Evandromyia sallesi and Nyssomyia intermedia species. More studies will be necessary to indentify whether these species are really incriminated in the urban transmission of the parasites in the urban areas. This study indicates the places of the spatio-temporal greatest occurrence and transmission of the disease in the urban zones of Barreiras city.

Transmission of Leishmania infantum from cats to dogs

Leishmania infantum infection in cats has been reported in several countries, including Brazil. However, the transmission of visceral leishmaniasis (VL) from cats to another host has not been proven yet. Therefore, the aim of this study was to verify the possibility of L. infantum transmission from cats to dogs. In order to verify the possibility of VL transmission from the cat to the dog, xenodiagnosis was carried out in a VL-positive cat, using 55 female Lutzomyia longipalpis. Five days later, 40 insects were dissected to verify Leishmania infection. The remaining 15 females were fed in a healthy dog. The potential infection of the dog was verified through clinical, serological, parasitological examinations, and PCR, at three, six, and twelve months post-infection. All 55 L. longipalpis females became visibly engorged. Leishmania promastigotes were detected in 27.5% of the dissected insects. Leishmania infection in the dog was confirmed upon first evaluation. DNA sequencing of the parasite isolated from the cat confirmed L. infantum infection and showed 99% similarity with the L. infantum DNA sequences from the dogs. Through this study, it was possible to confirm the L. infantum experimental transmission from a domestic cat to a domestic dog through its biological vector L. longipalpis.

Tanatopolítica e biossegurança: dois regimes de governo da vida para a leishmaniose visceral canina no Brasil

Resumo Apesar de ter sua legitimidade contestada nas últimas décadas por defensores de animais, juristas e veterinários que defendem o direito à vida e ao tratamento, assim como por pesquisadores da área da saúde que duvidam de sua eficácia, a “eutanásia profilática” massiva de cães testados como soropositivos para leishmaniose visceral mantém-se firme como política sanitária no Brasil. A partir da análise de documentos oficiais, revisão da literatura, comentários sobre processos judiciais colhidos na imprensa e da etnografia dos impactos do surto de leishmaniose visceral em Porto Alegre, este artigo visa compreender o que está em jogo nessa controvérsia, considerando seus aspectos discursivos na construção de moralidades e práticas biopolíticas. Sugere-se a existência de dois regimes de governo da vida na gestão dos reservatórios caninos da leishmaniose visceral: um tanatopolítico, ligado ao poder público; o outro, um dispositivo emergente de biossegurança, ligado ao mercado farmacêutico e acessível apenas para tratamento privado.

Effectiveness of insecticide-impregnated collars for the control of canine visceral leishmaniasis

Visceral leishmaniasis is a neglected tropical disease widely distributed worldwide. In Brazil, the control measures adopted in the last decades have not been able to prevent the spread of the disease. This study aimed to evaluate the effectiveness of a population-based intervention using 4% deltamethrin-impregnated dog collars on the incidence of canine visceral leishmaniasis. A community intervention study was carried out in two areas of the city of Montes Claros, State of Minas Gerais, Brazil. In the control area, the preventive measures recommended by the Brazilian Program for Surveillance and Control of Visceral Leishmaniasis were implemented (culling of infected dogs and vector control with residual insecticides). In the intervention area, deltamethrin-impregnated collars were fit to domiciled dogs, in addition to the above mentioned preventive measures. At the beginning of the study, a census survey was carried out among domiciled dogs to detect the prevalence of L. infantum infection. Dogs found seronegative at recruitment were longitudinally followed-up to evaluate the incidence of infection. Monitoring of canine infection (control and intervention areas) and replacement of collars (intervention area) occurred through sequential surveys at 12, 18, and 24 months after the initial survey. At each survey, dogs were tested, and the owner answered a questionnaire about the general characteristics of the animal. Multilevel logistic regression models were used to test the effect of collars on the risk of canine infection, with households considered as aggregation units. Associations were expressed as odds ratios (OR) and respective 95% confidence intervals (95%CI). The prevalence of infection in the initial survey was 9.7% and 9.9% in the intervention and control areas, respectively (p = 0.732). Among a total of 20,477 dogs participating in the study, 9,770 were seronegative at recruitment. The cumulative incidence of infection was 4.1% in the intervention area and 7.9% in the control area (p < 0.001). In the multivariable analysis, the risk of infection was 52% lower in the intervention area as compared to the control area (OR = 0.48, 95%CI:0.39-0.59), after adjusting for the number of dogs in the house, period of recruitment, time of dog ownership, and age, sex, length of fur and breed. The use of 4% deltamethrin-impregnated dog collars was effective in reducing the incidence of canine leishmaniasis. Cost-effectiveness studies are recommended before the incorporation of collars in the arsenal of control measures of the Brazilian Program for Surveillance and Control of Visceral Leishmaniasis.

Dogs with divergent serology for visceral leishmaniasis as sources of Leishmania infection for Lutzomyia longipalpis phlebotomine sand flies - an observational study in an endemic area in Brazil

Visceral leishmaniasis (VL) is a neglected tropical disease, caused by Leishmania (Kinetoplastida, Trypanosomatidae) species. In Brazil, the transmission of this parasite essentially occurs through the bite of Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae) previously infected with Leishmania infantum. Aiming at preventing VL expansion over the country, integrated control actions have been implemented through a Visceral Leishmaniasis Surveillance and Control Program (VLSCP). Among the actions currently adopted by the program, the screening-culling of seropositive dogs for canine VL (CVL) is particularly polemic. Dogs with negative or divergent serology for CVL remain in their owner’s domicile and are monitored by public health agents. In the present study, we determined the prevalence of CVL and analyzed the implementation of the VLSCP screening-culling action, in an area in Brazil where there has been a recent expansion of VL. Canine census surveys were conducted semiannually for two years (Aug/2015 to Feb/2017). Serological diagnosis of CVL was performed in accordance with current VLSCP protocol: immunochromatography (TR-DPP) followed by enzyme-linked immunosorbent assay (ELISA EIE). 6,667 dogs were serologically screened for CVL, of which 567 (8.5%) were positive in both tests and 641 (9.6%) had divergent results. A variable percentage (6.3% to 65.4%) of the dogs in the latter group became positive within nine months from the first result. Xenodiagnosis was conducted in canine samples belonging to any of the three possible serological statuses for CVL–positive, divergent or negative. Leishmania spp. DNA was detected in Lu. longipalpis that fed on 50.0% (5/10) of dogs with positive serology and on 29.4% (5/17) of dogs with divergent serological status for CVL. Therefore, dogs with divergent serology for CVL may be as Leishmania-infective to Lu. longipalpis as seropositive ones. Even with the adoption of euthanasia for seropositive dogs, part of the canine population will continue to serve as a source of Leishmania infection for phlebotomine sand flies.

Visceral leishmaniasis (VL) is a neglected tropical disease caused by a protozoan of the genus Leishmania. In Brazil, the parasites are mainly transmitted through the bite of female Lutzomyia longipalpis sand flies that have been previously infected with Leishmania infantum. Dogs are the main domestic reservoirs of Leishmania. The Brazilian Ministry of Health has implemented euthanasia of VL-seropositive dogs as a measure to prevent VL expansion in the country, using the Dual-Path Platform Immunochromatographic Rapid Test (TR-DPP) as the screening method and the enzyme-linked immunoassay (ELISA EIE) as the confirmatory test for diagnosis. Dogs with positive results in both tests are considered seropositive and recommended for euthanasia. Dogs with divergent serology between these tests remain at their owners’ home and part of them become seropositive within months. Therefore, even adopting euthanasia of seropositive dogs, part of the canine population will continue to serve as a source of Leishmania infection for sand flies, causing new canine and / or human cases of the disease. Difficulties and limitations to implement the screening-culling policy are also discussed.

Factors associated with Leishmania spp. infection in domestic dogs from an emerging area of high endemicity for visceral leishmaniasis in Central-Western Brazil

The factors associated with Leishmania spp. infection in dogs are still poorly understood. This study aimed to identify such factors among domestic dogs from the Brazilian municipality of Rondonópolis, which recently emerged as an endemic area with intense transmission of human visceral leishmaniasis (VL). It was a household-based cross-sectional study conducted between 2016 and 2017. Interviews were conducted with 405 dog owners considering their socioeconomic characteristics, and environmental aspects of the household and its adjacent areas. In addition, 600 dogs were evaluated regarding physical characteristics, behavior, and care provided by the owner. Seropositive animals were those that showed reactivity in a rapid immunochromatographic test and enzyme-linked immunosorbent assay, which are currently recommended for canine visceral leishmaniasis (CVL) diagnosis in Brazil. A multivariable logistic regression analysis was employed to determine the associated factors. Low social class [OR = 2.0; _95%CI = (1.2-3.2)], presence of acerola tree (Malpighia emarginata) in the yard [OR = 2.2; _95%CI = (1.2-4.1)], presence of more than one dog in the household [OR = 2.0; _95%CI = (1.3-3.3)], horse and/or cattle breeding [OR = 12.0; _95%CI = (1.9-73.6)], existence of houses with yard adjacent to the home [OR = 4.0; _95%CI = (1.3-12.2)], presence of apparent signs consistent with CVL [OR = 10.6; _95%CI = (5.8-19.4)], dog staying mostly in the yard during the day [(OR = 4.8; _95%CI = (1.1-21.4)], and lack of cleaning of the dog's shelter [(OR = 1.9; _95%CI = (1.1-3.2)] were identified as the factors associated with Leishmania spp. infection. These results support the importance of socioeconomic and environmental aspects in the occurrence of Leishmania spp. infection. In addition, they may be useful in guiding control strategies in areas where zoonotic VL is endemic.

Human visceral leishmaniasis and relationship with vector and canine control measures

OBJECTIVE

Estimate the coverage of control measures of visceral leishmaniasis and relate them with the occurrence of human visceral leishmaniasis in endemic urban area.

METHODS

Cases of human and canine visceral leishmaniasis were considered as study population and evaluated by a serological survey conducted in Araçatuba, state São Paulo, from 2007 to 2015. The cases of human visceral leishmaniasis were geocoded by the address of the patients and the canine disease by the address of the dogs’ owners. The coverage of serological survey, euthanasia, and insecticide spraying was calculated, as well as the canine seroprevalence and the incidence rates of human visceral leishmaniasis. The relationship between human visceral leishmaniasis and control measures was evaluated, as well as the seroprevalence by comparing maps and by linear regression. The relationship between the canine and the human disease was also evaluated by the Ripley’s K function.

RESULTS

The incidence rates of human visceral leishmaniasis showed a period of decline (2007 to 2009) and a period of stability (2010 to 2015), a behavior similar to that of canine seroprevalence. In general, the coverage of control measures was low, and the non-association with the incidence of human visceral leishmaniasis can be a result of the period analyzed and of the small number of analyzed units (sectors of the Superintendence for the Control of Endemic Diseases). The distribution of human cases showed spatial dependence with the distribution of seropositive dogs from 2007 to 2009.

CONCLUSIONS

This study reaffirmed the relationship between the occurrence of the disease in humans and dogs, it verified a decrease in the rates of visceral leishmaniasis in Araçatuba over time, even at low coverage of control activities. However, further studies are needed to determine if factors beyond monitoring and control measures are involved in the reduction of incidences.

Epidemiology of human visceral leishmaniasis in the urban centers of the lower-middle São Francisco Valley, Brazilian semiarid region

INTRODUCTION

Visceral leishmaniasis (VL) is a zoonosis caused by parasites of the Leishmania genus. VL is present in countries with tropical climates, being endemic in Brazil,, including the region of the lower-middle São Francisco Valley which includes the urban centers of Petrolina (Pernambuco state) and Juazeiro (Bahia state).

METHODS

This retrospective and descriptive epidemiological study analyzed secondary data obtained from the mandatory visceral leishmaniasis notification forms of the Ministry of Health, which were compiled in the Information System for Notifiable Diseases (SINAN) database. We analyzed 181 autochthonous cases reported in the two aforementioned cities between 2010 and 2016. Data collection occurred in June 2017.

RESULTS

Of the 181 VL cases in the study area, 40.9% (n=74) occurred in Juazeiro and 59.1% (n=107) occurred in Petrolina. The average numbers of cases per year were 9.5 in Juazeiro and 14 in Petrolina; respectively, the incidence ranges were 2-8.6 cases and 2.8-6.1 cases per 100,000 inhabitants. Fever, weakness, weight loss, and pallor were the most commonly observed clinical manifestations. Coinfection with human immunodeficiency virus (HIV) was observed in 16.8% and 5.4% of cases in Petrolina and Juazeiro, respectively. The lethality rates were 2.8% and 5.4% in Petrolina and Juazeiro, respectively.

CONCLUSIONS

Both cities had a high incidence of VL during the studied period. The findings of this study contribute to a better understanding of the behavior of VL during recent years and may help to direct regional disease control measures.

The mass use of deltamethrin collars to control and prevent canine visceral leishmaniasis: A field effectiveness study in a highly endemic area

Background

Visceral leishmaniasis (VL) is a zoonosis of great importance. Limitations in current VL control measures compromise efficacy, indicating the need to implement new strategies. The aim of this study was to evaluate the effectiveness of the mass use of deltamethrin-impregnated collars in dogs as a public health measure to control and prevent canine visceral leishmaniasis (CVL).

Methodology

An interventional study was implemented in two endemic areas in the district of Monte Gordo (Bahia-Brazil): an intervention area, in which VL seronegative dogs were collared, and a control area in which only conventional CVL control measures were applied. At baseline, seropositive dogs were removed and seronegative dogs were included. Dogs were then reevaluated every 7–8 months for almost two years. At each time point, dogs in the intervention area that remained seronegative received new collars and newly identified seronegative dogs were included and collared. The local zoonosis control authorities were notified of any dogs that tested seropositive in both areas, which were subsequently marked for euthanasia as mandated by the Brazilian Ministry of Health.

Principal findings

In the first serological survey, seroprevalence was similar in both areas. At the second evaluation, significant reductions in seroprevalence were seen in both areas, while seroprevalence in the intervention area reduced to 6.0% during the final evaluation versus an increase of 11.0% in the control area. This significant increase and the estimated relative risk (RR = 0.55) indicated protection against CVL in the intervention area. Although CVL incidence did not differ significantly between the areas, an increased tendency was observed in the control area, which could be due to low seroconversion rates throughout the study or a high loss to follow-up.

Conclusions/Significance

Although our evaluation of the effectiveness of deltamethrin-impregnated collars as a community-wide public health control measure was inconclusive, this measure likely provides protection over time. In endemic areas of Brazil, this strategy represents an operational challenge for local zoonosis control authorities, indicating the need for adjustments, including improved collar design.

Visceral leishmaniasis (VL) is a serious public health problem. Cases of canine VL (CVL) tend to precede cases of human VL and current control measures are ineffective in significantly reducing the number of disease cases. Therefore, in light of the need for new strategies, we evaluated the mass use of dog collars impregnated with deltamethrin as a public health measure to control and prevent CVL in a highly endemic region in Brazil. Although our results were inconclusive, they do point to the possible effectiveness of this measure if it were comprehensively implemented over an extended period of time. We identified the need to adjust the currently employed implementation strategy and call attention to the operational challenges faced by local zoonosis prevention authorities.

High seroprevalence and peripheral spatial distribution of visceral leishmaniasis among domestic dogs in an emerging urban focus in Central Brazil: a cross-sectional study

The Brazilian municipality of Rondonópolis is an emerging urban focus of intense transmission of visceral leishmaniasis (VL), where few investigations have addressed canine reservoirs. This study assessed the seroprevalence and spatial distribution of canine visceral leishmaniasis (CVL) in the urban area of Rondonópolis. A CVL serosurvey was conducted between October 2016 and February 2017 using an immunochromatographic rapid test and enzyme-linked immunosorbent assay. Domestic dogs were sampled from 25 heterogeneous regions previously defined by the Spatial 'K'luster Analysis by Tree Edge Removal algorithm, which considered the socioeconomic and environmental features from the last demographic census. The CVL spatial distribution was analyzed by kernel density estimation (KDE) and spatial scan statistic. All the  autochthonous human VL cases reported between 2014 and 2016 were georeferenced. Of the 600 dogs tested, 115 were seropositive in both tests. The overall CVL prevalence was 19.2% (95%CI: 16.1-22.3%), which varied widely among the evaluated regions (0.0-35.1%). Almost 25% of the sampled households (n = 405) had at least one infected dog. KDE demonstrated that positive CVL households were concentrated in the peripheral areas of the city. Spatial scan statistics detected a spatial cluster with significantly low CVL prevalence in the central region (relative risk = 0.37; p = 0.04), where only one human VL case was reported. Thus, we demonstrated a high prevalence of CVL in domestic dogs from diverse socioeconomic and environmental urban contexts in Rondonópolis. The CVL cases were peripherally distributed and occurred more frequently in areas that had reported human VL.

Fatores ambientais associados à ocorrência de leishmaniose visceral canina em uma área de recente introdução da doença no Estado do Rio de Janeiro, Brasil

Resumo: Foi avaliada a associação entre características ambientais obtidas por sensoriamento remoto e a prevalência da leishmaniose visceral canina (LVC) no bairro do Jacaré, área de recente introdução da doença, no Município de Niterói, Estado do Rio de Janeiro, Brasil. Trata-se de um estudo seccional para avaliação da prevalência de LVC, definida por meio da positividade no teste imunocromatográfico rápido em dupla plataforma (dual path platform - DPP), confirmada com o ensaio imunoenzimático (EIE). Foram incluídos 97 cães com prevalência de LVC de 21,6%. Houve maior frequência de LVC em cães com a convivência com outro cão, gambá, mico e ouriço-terrestre, assim como com a história de remoção de outros cães com LVC do domicílio. Na análise multivariada, ajustada por sexo e idade do cão, cães residentes em áreas com maior cobertura de vegetação esparsa apresentaram prevalência da infecção por Leishmania infantum cinco vezes maior do que aqueles que residiam em áreas menos vegetadas (OR = 5,72; IC95%: 1,47-22,20). Por outro lado, áreas mais urbanizadas caracterizadas como comerciais ou residenciais carentes, identificadas pelo sensoriamento remoto como aquelas com alta densidade de estruturas cinza, estiveram associadas à menor ocorrência da LVC (OR = 0,09; IC95%: 0,01-0,92). A maior prevalência de infecção em cães convivendo com outros animais silvestres e em áreas com maior cobertura vegetal, associada com menor prevalência em áreas urbanizadas, indica um padrão rural de transmissão da LVC nessa área.

Evaluation of chemical spraying and environmental management efficacy in areas with minor previous application of integrated control actions for visceral leishmaniasis in Brazil

Leishmaniases are vector-borne diseases that are transmitted to humans through the bite of Leishmania-infected phlebotomine sand flies (Diptera:Psychodidae). The main proved vector of visceral leishmaniais (VL) in the New World - Lutzomyia longipalpis - is well-adapted to urban areas and has extensive distribution within the five geographical regions of Brazil. Integrated public health actions directed for the vector, domestic reservoir and humans for the control of VL are preferentially applied in municipalities with higher epidemiological risk of transmission. In this study, we evaluated the individual impact of two main vector control actions - chemical spraying and environmental management - in two districts with no reported cases of human VL. Although belonging to an endemic municipality for VL in Brazil, the integrated control actions have not been applied in these districts due to the absence of human cases. The number of L. longipalpis captured in a two-year period was used as indicator of the population density of the vector. After chemical spraying a tendency of reduction in L. longipalpis was observed but with no statistical significance compared to the control. Environmental management was effective in that reduction and it may help in the control of VL by reducing the population density of the vector in a preventive and more permanent action, perhaps associated with chemical spraying.

Uso e cobertura do solo e prevalência de leishmaniose visceral canina em Teresina, Piauí, Brasil: uma abordagem utilizando sensoriamento remoto orbital

Resumo: Este estudo examina a associação entre uso e cobertura do solo e a ocorrência de leishmaniose visceral (LV) canina. Estudo caso-controle em que casos foram residências com cães soropositivos para LV canina e controles, as residências com cães soronegativos. Utilizaram-se imagens de sensoriamento remoto (CBERS: 2/CCD e 2B/HRC) para descrever o uso e cobertura do solo em quadrículas de 625m2 na região do estudo. A chance da LV canina foi duas vezes maior em domicílios localizados em quadrículas com área ≤ 25m2 coberta por estruturas residenciais com pouca vegetação em comparação com aquelas em que essa cobertura alcançou ≥ 600m2. Domicílios localizados em quadrículas com até metade da área coberta por estruturas residenciais com muita vegetação tiveram chances 65% menores de LV canina em comparação com aquelas situadas em áreas quase totalmente cobertas por essa característica. Como a infecção canina costuma preceder a ocorrência de casos humanos, a identificação de características de uso e cobertura do solo associadas à LV canina pode contribuir para a delimitação de áreas de risco para LV humana.

Neglected tropical diseases in Brazilian children and adolescents: data analysis from 2009 to 2013

BACKGROUND

Neglected tropical diseases (NTDs) prevail in conditions of poverty and contribute to the maintenance of social inequality. Out of the NTDs prioritized by the Brazilian Ministry of Health, four parasitic infections require mandatory notification: acute Chagas disease, leishmaniasis, malaria, and schistosomiasis. Data on the behaviour of these NTDs in the young population are currently limited. This study seeks to analyse the epidemiological aspects of these parasitic infections in children and adolescents in Brazil.

METHODS

A retrospective exploratory ecological study was conducted. A spatial analysis of the cases reported between 2009 and 2013 in individuals aged between 0 and 19 years that were notified through the Health Notification Aggravation Information System (SINAN) was performed.

RESULTS

In total, 64,567 cases of cutaneous and visceral leishmaniasis, malaria, schistosomiasis, and acute Chagas disease were recorded in the SINAN database, representing a rate of 20.15 cases per 100,000 inhabitants. The average age of the cases was 12.2 years and 62.32% were male. Four hundred and three deaths related to these obligatorily reported parasites were recorded, indicating a case fatality rate of 0.62%. Visceral leishmaniasis and acute Chagas disease had the highest rates of lethality. A heterogeneous spatial distribution of the studied parasites was observed.

CONCLUSIONS

The number of cases and the lethality rate described in this study show that these diseases still represent a serious problem for public health in Brazil. This points to the need to encourage new research and the reformulation of social, economic, and public health policies aimed at ensuring better health and living conditions for all individuals, especially those among the populations considered vulnerable, as is the case of the young.

Further evidence associating IgG1, but not IgG2, with susceptibility to canine visceral leishmaniasis caused by Leishmania (L.) infantum chagasi-infection

We present here a cross-sectional study analyzing the IgG1 and IgG2 immune responses to natural canine Leishmania (L.) infantum chagasi-infection and their relationships with delayed-type hypersensitivity (DTH) in 50 mongrel dogs with previous positive serodiagnoses (IFAT-IgG) (56% with subclinical status [= apparently healthy] and 44% clinically sick), living in endemic areas for visceral leishmaniasis in the Brazilian Amazon. IgG1 and IgG2 responses were measured using commercial polyclonal antibodies in ELISA, while DTH was elicited by intradermal skin test using cultured promastigotes L. (L.) i. chagasi-antigen. Data analyses used Chi-square and Pearson's r coefficient (95% confidence interval). Regarding DTH and the clinical statuses of dogs, it was noted that 100% of the animals showing positive DTH (n = 8) were from the subclinical group, while 100% showing negative DTH were from the clinically sick group; higher IgG2 than IgG1 responses were observed in both clinical groups. However, when this comparison was made between the subclinical and sick groups, higher IgG1 responses were noted in the dogs from the sick rather than the subclinical group, while no differences were noted between the IgG2 responses in the dogs from both clinical groups. Additionally, we found lower IgG1 responses in dogs from the subclinical group showing positive DTH than in the dogs from the subclinical or sick groups with negative DTH; no differences were found between the IgG2 responses of these two clinical groups. These findings suggest that the IgG1, but not the IgG2, response is associated with susceptibility to canine visceral leishmaniasis (CVL).

Perceptions of the population and health professionals regarding visceral leishmaniasis

Based on theoretical qualitative research reference methodology, this study sought to investigate the perception of visceral leishmaniasis (VL) by social actors directly involved in the prevention and control of the disease. Thirty-eight semi-structured interviews were conducted with residents, focus groups were staged with 18 health workers in an endemic VL area and depositions were collected, which after being processed by content analysis revealed shortcomings and challenges. The population associated VL with dogs, acknowledged their co-responsibility in tackling the disease and demanded information. Health workers identified environmental sanitation as an essential factor for VL prevention. Among the shortcomings, the lack of information about the disease and culpability of the individual because of non-adherence to prevention measures were observed, especially environmental management. Probably, approaches emphasizing the role of the environment as a health promotion agent and the timely definition of specific environmental measures against VL, constitute a prospect for overcoming these shortcomings. The consensus is that the main challenge for enhancing the prevention and control might be the participatory and dialogical construction of these approaches between health professionals and the population.

Leishmania infantum INFECTION IN DOGS FROM THE SOUTHERN REGION OF MINAS GERAIS STATE, BRAZIL

Visceral leishmaniasis is a systemic and chronic disease and dogs are the main reservoir of the etiologic agent, Leishmania infantum (syn L. chagasi). A serological and molecular investigation of canine visceral leishmaniasis (CVL) was performed in the municipality of Alfenas, located in the southern region of Minas Gerais, where the disease is not endemic. Samples from 87 dogs were submitted to serological tests including the Dual Path Platform (DPP^(r) ) CVL Bio-Manguinhos rapid test, an in-house enzyme-linked immunosorbent assay (ELISA) and an immunofluorescence antibody test (IFAT), as well as molecular techniques such as a conventional polymerase chain reaction (PCR) with the RV1/RV2 primers and a quantitative PCR (qPCR) with the LinJ31, Ldon and DNApol primers. Of the 87 serum samples, eight (9.2%) were positive for Leishmania using the DPP rapid test, but only four (4.6%) were confirmed by ELISA and two (2.3%) by IFAT. In these two serologically confirmed cases, spleen and liver samples were positive by all the employed molecular and parasitological procedures performed on spleen samples. When whole blood samples were used in the molecular assays, two samples (2.3%) were positive only by qPCR. DNA extracted and amplified from the spleens of seropositive dogs was sequenced, showing 100% of similarity with the Leishmania infantum (syn L. chagasi) sequence. Thus, the first cases of CVL have been confirmed in the Alfenas region, suggesting the importance of canine surveys in non-endemic municipalities for CVL to monitor disease progression and to prevent outbreaks.

VISCERAL LEISHMANIASIS IN PETROLINA, STATE OF PERNAMBUCO, BRAZIL, 2007-2013

Visceral leishmaniasis is a life-threatening disease of great public health relevance in Brazil. The municipality of Petrolina is an endemic area in the State of Pernambuco, Brazil. This study was designed to assess the recent expansion of VL in the municipality of Petrolina, Pernambuco. Patients data were obtained from the Brazilian National Information System for Notifiable Diseases (SINAN). A total of 111 records from 2007 to 2013 were investigated, of which 69 were residents in Petrolina. The disease has predominantly affected 1-4 year old children (34.8%). Most of the patients were males (59.4%). Co-infection with human immunodeficiency virus occurred in 14.5% of the cases. The criterion most frequently used was the clinical and epidemiological confirmation (59.4%), with clinical cure in 78.3% of cases and one fatal outcome. Visceral leishmaniasis is endemic in Petrolina with transmission levels varying from moderate to high. The present study has shown the precariousness of the use of diagnostic tests in primary healthcare units, and this misuse has interfered with the diagnosis and treatment of cases.

Lutzomyia longipalpis urbanisation and control

Since the description of Lutzomyia longipalpis by Lutz and Neiva more than 100 years ago, much has been written in the scientific literature about this phlebotomine species. Soares and Turco (2003) and Lainson and Rangel (2005) have written extensive reviews focused on vector-host-parasite interactions and American visceral leishmaniasis ecology. However, during the last two decades, the success of Lu. longipalpis in colonising urban environments and its simultaneous geographical spreading have led to new theoretical and operational questions. Therefore, this review updates the general information about this species and notes the more challenging topics regarding the new scenario of urbanisation-spreading and its control in America. Here, we summarise the literature on these issues and the remaining unsolved questions, which pose recommendations for operational research.

Historical series of patients with visceral leishmaniasis treated with meglumine antimoniate in a hospital for tropical diseases, Maceió-AL, Brazil

INTRODUCTION

Visceral leishmaniasis is an endemic protozoan found in Brazil. It is characterized by fever, pallor, hepatosplenomegaly, lymphadenopathy, and progressive weakness in the patient. It may lead to death if untreated. The drug of choice for treatment is meglumine antimoniate (Glucantime). The aim of this study was to evaluate patients with visceral leishmaniasis according to criteria used for diagnosis, possible reactions to Glucantime and blood pressure measured before and after treatment.

METHODS

89 patients admitted to the Teaching Hospital Dr. Hélvio Auto (HEHA) in Maceió-AL, in the period from May 2006 to December 2009 were evaluated. Data were collected on age, sex, origin, method of diagnosis, adverse effects of drugs, duration of hospitalization, duration of treatment and dosage up to the onset of adverse effects.

RESULTS

There was a predominance of child male patients, aged between one and five years old, from the interior of the State of Alagoas. Parasitological diagnosis was made by bone marrow aspirate; three (3.37%) patients died, 12 (13.48%) had adverse reactions and treatment was changed to amphotericin B, and 74 (83.14%) were cured. Changes that led to replacing Glucantime were persistent fever, jaundice, rash, bleeding and cyanosis.

CONCLUSION

During the study, 89 patients hospitalized for VL were analyzed: 74 were healed, 12 were replaced by amphotericin B treatment and three died. Most of them were under five years old, male and came from the interior. The dosage and duration of treatment with Glucantime were consistent with that advocated by the Ministry of Health. Persistence of fever, jaundice, rash, cyanosis and bleeding were the reactions that led the physician to modify treatment. No change was observed in blood pressure before and after treatment. This study demonstrated the work of a hospital, a reference in the treatment of leishmaniasis, which has many patients demanding its services in this area. It demonstrates that this disease is still important today, and needs to be addressed properly to prevent injury and death due to the disease.

Canine visceral leishmaniasis in an urban setting of Southeastern Brazil: an ecological study involving spatial analysis

Background

The physical characteristics of the environment influence the composition, distribution and behavior of the vectors and mammalian hosts involved in the transmission of visceral leishmaniasis (VL), thereby affecting the epidemiology of the disease. In Brazil, urbanization of human VL is a recent phenomenon and represents an issue of particular concern to local health authorities. The present study aimed to establish the degree of spatial dependency between canine and human VL in the municipality of Divinópolis, Minas Gerais, Brazil, and to identify priority risk areas in which stricter control measures should be implemented.

Methods

The selected canine population comprised 3,652 dogs distributed within 11 strata and 1,247 urban blocks. Serum samples were collected between March 2013 and February 2014. Serodiagnosis of dogs was performed using the enzyme-linked immunosorbent assay and the indirect fluorescent-antibody test. The blocks sampled for canine VL and the addresses of the 16 confirmed cases of human VL notified in Divinópolis during the period 2007–2013 were georeferenced. Spatial analysis of the data was performed using Kernel density estimation, Ripley’s bivariate K-function and directional distribution methods.

Results

The overall prevalence of seropositive animals was 4.63% (range 3.95 - 5.31) (n =169) and varied in different strata between 0.9 (range 0.0 - 1.91) and 8.73% (range 5.65 - 11.81). A positive spatial dependency was detected between human and canine VL in which the occurrence of human cases of the disease tended to concentrate in locations that were close to areas with a higher incidence of canine VL. The priority risk area could be clearly distinguished from Kernel density estimation and standard deviational ellipse plots in which the human VL ellipse was totally enclosed within the canine VL ellipse.

Conclusions

The results presented herein will enable the Municipal Health Office of Divinópolis to devise a more effective management plan for human VL in which specific strategies would be applied to areas presenting different levels of risk. This spatial evaluation of leishmaniasis model could be applied in other urban areas of Brazil.

Mortality and case fatality due to visceral leishmaniasis in Brazil: a nationwide analysis of epidemiology, trends and spatial patterns

BACKGROUND

Visceral leishmaniasis (VL) is a significant public health problem in Brazil and several regions of the world. This study investigated the magnitude, temporal trends and spatial distribution of mortality related to VL in Brazil.

METHODS

We performed a study based on secondary data obtained from the Brazilian Mortality Information System. We included all deaths in Brazil from 2000 to 2011, in which VL was recorded as cause of death. We present epidemiological characteristics, trend analysis of mortality and case fatality rates by joinpoint regression models, and spatial analysis using municipalities as geographical units of analysis.

RESULTS

In the study period, 12,491,280 deaths were recorded in Brazil. VL was mentioned in 3,322 (0.03%) deaths. Average annual age-adjusted mortality rate was 0.15 deaths per 100,000 inhabitants and case fatality rate 8.1%. Highest mortality rates were observed in males (0.19 deaths/100,000 inhabitants), <1 year-olds (1.03 deaths/100,000 inhabitants) and residents in Northeast region (0.30 deaths/100,000 inhabitants). Highest case fatality rates were observed in males (8.8%), ≥ 70 year-olds (43.8%) and residents in South region (17.7%). Mortality and case fatality rates showed a significant increase in Brazil over the period, with different patterns between regions: increasing mortality rates in the North (Annual Percent Change--APC: 9.4%; 95% confidence interval--CI: 5.3 to 13.6), and Southeast (APC: 8.1%; 95% CI: 2.6 to 13.9); and increasing case fatality rates in the Northeast (APC: 4.0%; 95% CI: 0.8 to 7.4). Spatial analysis identified a major cluster of high mortality encompassing a wide geographic range in North and Northeast Brazil.

CONCLUSIONS

Despite ongoing control strategies, mortality related to VL in Brazil is increasing. Mortality and case fatality vary considerably between regions, and surveillance and control measures should be prioritized in high-risk clusters. Early diagnosis and treatment are fundamental strategies for reducing case fatality of VL in Brazil.

Use of a recombinant cysteine proteinase from Leishmania (Leishmania) infantum chagasi for the Immunotherapy of canine visceral Leishmaniasis

BACKGROUND

A recombinant cysteine proteinase from Leishmania (Leishmania) infantum chagasi (rLdccys1) was previously shown to induce protective immune responses against murine and canine visceral leishmaniasis. These findings encouraged us to use rLdccys1 in the immunotherapy of naturally infected dogs from Teresina, Piauí, a region of high incidence of visceral leishmaniasis in Brazil.

METHODOLOGY/PRINCIPAL FINDINGS

Thirty naturally infected mongrel dogs displaying clinical signs of visceral leishmaniasis were randomly divided in three groups: one group received three doses of rLdccys1 in combination with the adjuvant Propionibacterium acnes at one month interval between each dose; a second group received three doses of P. acnes alone; a third group received saline. The main findings were: 1) dogs that received rLdccys1 with P. acnes did not display increase of the following clinical signs: weight loss, alopecia, onychogryphosis, cachexia, anorexia, apathy, skin lesions, hyperkeratosis, ocular secretion, and enlarged lymph nodes; they also exhibited a significant reduction in the spleen parasite load in comparison to the control dogs; 2) rLdccys1-treated dogs exhibited a significant delayed type cutaneous hypersensitivity elicited by the recombinant antigen, as well as high IgG2 serum titers and low IgG1 serum titers; sera from rLdccys1-treated dogs also contained high IFN-γ and low IL-10 concentrations; 3) control dogs exhibited all of the clinical signs of visceral leishmaniasis and had low serum IgG2 and IFN-γ levels and high concentrations of IgG1 and IL-10; 4) all of the dogs treated with rLdccys1 were alive 12 months after treatment, whereas dogs which received either saline or P. acnes alone died within 3 to 7 months.

CONCLUSIONS/SIGNIFICANCE

These findings illustrate the potential use of rLdccys1 as an additional tool for the immunotherapy of canine visceral leishmaniasis and support further studies designed to improve the efficacy of this recombinant antigen for the treatment of this neglected disease.

Spatial analysis for identification of priority areas for surveillance and control in a visceral leishmaniasis endemic area in Brazil

Spatial analysis of epidemiological data may be used to assist in the implementation of surveillance and control measures against visceral leishmaniasis (VL) in endemic areas. This ecological study aimed to identify priority areas for surveillance and control of VL in São Luís, the capital of the state of Maranhão in northeast Brazil, a highly endemic area for the disease. We evaluated the spatial structure of the incidence rates of human VL and of the mean number of human and canine cases occurring between 2005 and 2007 in 355 neighborhoods (aggregated into 203 geographical analytical units) within the municipality. The presence of spatial autocorrelation was explored using global and local Moran's I statistics. A local indicator of spatial autocorrelation was used to generate maps for the identification of VL clusters. The global Moran's I index revealed a weak, but statistically significant spatial autocorrelation for human VL incidence rates (I=0.138). A total of 43 geographical analytical units, encompassing 121 neighborhoods, were identified as priority areas for implementing surveillance and control actions. For the purpose of defining an action plan for the delivery of these measures, those 16 geographical analytical units (encompassing 54 neighborhoods) identified as clusters with high incidence rates of human VL should receive the highest priority. An additional nine geographical analytical units (comprising 28 neighborhoods) showed non-significant clustering of high rates of human, and might be considered as the next priority for VL management. Finally, a further 18 geographical analytical units (covering 39 neighborhoods) had records of coexisting human and canine VL cases during the study period, and these should receive priority attention when resources become available. Spatial data analysis is a valuable tool for defining priority areas for VL surveillance in high transmission areas contributing to a more effective management of financial and technical resources, increasing the sustainability and efficiency of control efforts.

Heterogeneities in Leishmania infantum infection: using skin parasite burdens to identify highly infectious dogs

Background

The relationships between heterogeneities in host infection and infectiousness (transmission to arthropod vectors) can provide important insights for disease management. Here, we quantify heterogeneities in Leishmania infantum parasite numbers in reservoir and non-reservoir host populations, and relate this to their infectiousness during natural infection. Tissue parasite number was evaluated as a potential surrogate marker of host transmission potential.

Methods

Parasite numbers were measured by qPCR in bone marrow and ear skin biopsies of 82 dogs and 34 crab-eating foxes collected during a longitudinal study in Amazon Brazil, for which previous data was available on infectiousness (by xenodiagnosis) and severity of infection.

Results

Parasite numbers were highly aggregated both between samples and between individuals. In dogs, total parasite abundance and relative numbers in ear skin compared to bone marrow increased with the duration and severity of infection. Infectiousness to the sandfly vector was associated with high parasite numbers; parasite number in skin was the best predictor of being infectious. Crab-eating foxes, which typically present asymptomatic infection and are non-infectious, had parasite numbers comparable to those of non-infectious dogs.

Conclusions

Skin parasite number provides an indirect marker of infectiousness, and could allow targeted control particularly of highly infectious dogs.

Zoonotic visceral leishmaniasis is a sandfly-borne disease of humans and dogs caused by the intracellular parasite Leishmania infantum. Dogs are the proven reservoir. The disease is usually fatal unless treated, and is of global health significance. Diagnosis of canine infections relies on serum antibody-based tests that measure infection. In some endemic regions, a test-and-slaughter policy of seropositive dogs forms part of the national control policy to reduce human infection. However, this strategy is not considered effective. Since not all infected dogs are infectious to sandfly vectors, one option is to target control at infectious dogs, as only these dogs maintain transmission. We quantify Leishmania numbers in individual host tissues from time of infection using molecular methods. Comparing these results with their infectiousness to sandflies, we also evaluate the performance of molecular and immunological assays to identify infectious animals. Parasite numbers varied substantially between individuals, increasing with duration and severity of disease. Infectiousness to the sandfly vector was associated with high parasite numbers, and parasite loads in the skin was the best predictor of being infectious. The results suggest that molecular quantitation is useful in identifying individuals and populations responsible for maintaining transmission, with potential application in operational control programmes.

Culling dogs in scenarios of imperfect control: realistic impact on the prevalence of canine visceral leishmaniasis

Background

Visceral leishmaniasis belongs to the list of neglected tropical diseases and is considered a public health problem worldwide. Spatial correlation between the occurrence of the disease in humans and high rates of canine infection suggests that in the presence of the vector, canine visceral leishmaniasis is the key factor for triggering transmission to humans. Despite the control strategies implemented, such as the sacrifice of infected dogs being put down, the incidence of American visceral leishmaniasis remains high in many Latin American countries.

Methodology/Principal Findings

Mathematical models were developed to describe the transmission dynamics of canine leishmaniasis and its control by culling. Using these models, imperfect control scenarios were implemented to verify the possible factors which alter the effectiveness of controlling this disease in practice.

Conclusions/Significance

A long-term continuous program targeting both asymptomatic and symptomatic dogs should be effective in controlling canine leishmaniasis in areas of low to moderate transmission (R₀ up to 1.4). However, the indiscriminate sacrifice of asymptomatic dogs with positive diagnosis may jeopardize the effectiveness of the control program, if tests with low specificity are used, increasing the chance of generating outrage in the population, and leading to lower adherence to the program. Therefore, culling must be planned accurately and implemented responsibly and never as a mechanical measure in large scale. In areas with higher transmission, culling alone is not an effective control strategy.

Visceral leishmaniasis is listed as a neglected tropical disease and is considered a public health problem worldwide. The disease has been documented since 1885, the first case being reported in India. After over 120 years, the incidence of the disease remains high despite control strategies implemented. In areas where the disease is zoonotic, such as in Brazil, identification as well as removal of infected dogs is recommended in highly endemic areas for they are considered to be the reservoir of the Leishmania chagasi parasite. The theoretical basis that supports the culling of infected dogs is the assumption that the incidence of human infection is directly related to the number of infectious dogs. However, there is no consensus among researchers on the effectiveness of this strategy for controlling either human or canine visceral leishmaniasis. In this context, mathematical models can provide a basis for determining the strategies with the greatest potential for success. This paper aims to contribute to this discussion by introducing further complexities into the problem, in particular, the imperfect diagnosis of this infection and the time gap between laboratory diagnosis and culling and the presence of asymptomatic infections.

Public Knowledge about and Detection of Canine Visceral Leishmaniasis in Urban Divinópolis, Brazil

Background. Leishmaniases are diseases with a wide spectrum of clinical manifestations including cutaneous (CL) and visceral (VL) forms. Many factors may affect their occurrence and expansion including environmental, geographic, and social conditions. In the past two decades, Divinópolis, Minas Gerais State, Brazil, has exhibited the potential for a disease outbreak, with the appearance of CL, and VL cases (human and canine). Hence, this study was initiated to monitor public knowledge of the disease. Questionnaires were administered in four neighborhoods (Jardim Belvedere, Esplanada, Danilo Passos I and II) where most of the human and canine cases have been reported. The analyses demonstrated that public knowledge of the disease is sparse and fragmented. A strong perception of the dog as the main reservoir was observed. Five veterinary clinics were evaluated for the presence of canine VL using serological (RIFI and ELISA) and molecular (PCR-RFLP) techniques. This is the first study demonstrating the occurrence of Leishmania infantum in Divinópolis, suggesting a possible urbanization of VL.

Canine skin and conjunctival swab samples for the detection and quantification of Leishmania infantum DNA in an endemic urban area in Brazil

BACKGROUND

We evaluated kDNA PCR/hybridization and quantitative real-time PCR (qPCR) targeting the gene of DNA polymerase of Leishmania infantum for CVL diagnosis and assessment of parasite load in clinical samples obtained invasively and non-invasively.

METHODOLOGY/PRINCIPAL FINDINGS

Eighty naturally infected dogs from an endemic urban area in Brazil were used. Animals were divided into two groups based on the presence or absence of CVL clinical sings. Skin biopsies, bone marrow, blood and conjunctival swabs samples were collected and submitted to L. infantum DNA detection. In addition, anti-Leishmania antibody titers were measured by Immunofluorescence antibody test. The symptomatic dogs had increased titers compared to asymptomatic dogs (P = 0.025). The frequencies of positive results obtained by kDNA PCR/hybridization for asymptomatic and symptomatic dogs, respectively, were as follows: right conjunctiva, 77.5% and 95.0%; left conjunctiva, 75.0% and 87.5%; skin, 45.0% and 75.0%; bone marrow, 50.0% and 77.5%; and blood, 27.5% and 22.5%. In both groups, the parasite load in the skin samples was the highest (P<0.0001). The parasite loads in the conjunctival swab and bone marrow samples were statistically equivalent within each group. The parasite burden in conjunctival swabs was higher in the dogs with clinical signs than in asymptomatic dogs (P = 0.028). This same relationship was also observed in the bone marrow samples (P = 0.002). No differences in amastigotes load in the skin were detected between the groups.

CONCLUSIONS

The conjunctival swab is a suitable clinical sample for qualitative molecular diagnosis of CVL. The highest parasite burdens were detected in skin regardless of the presence of VL-associated clinical signs. The qPCR results emphasized the role of dogs, particularly asymptomatic dogs, as reservoirs for CVL because of the high cutaneous parasite loads. These results may help to explain the maintenance of high transmission rates and numbers of CVL cases in endemic urban regions.

Prevalence and factors associated with Leishmania infantum infection of dogs from an urban area of Brazil as identified by molecular methods

Background

Various factors contribute to the urbanization of the visceral leishmaniasis (VL), including the difficulties of implementing control measures relating to the domestic reservoir. The aim of this study was to determine the prevalence of canine visceral leishmaniasis in an urban endemic area in Brazil and the factors associated with Leishmania infantum infection among seronegative and PCR-positive dogs.

Methodology

A cross-sectional study was conducted in Belo Horizonte, Minas Gerais, Brazil. Blood samples were collected from 1,443 dogs. Serology was carried out by using two enzyme-linked immunosorbent assays (Biomanguinhos/FIOCRUZ/RJ and “in house”), and molecular methods were developed, including PCR-RFLP. To identify the factors associated with early stages of infection, only seronegative (n = 1,213) animals were evaluated. These animals were divided into two groups: PCR-positive (n = 296) and PCR-negative (n = 917) for L. infantum DNA. A comparison of these two groups of dogs taking into consideration the characteristics of the animals and their owners was performed. A mixed logistic regression model was used to identify factors associated with L. infantum infection.

Principal Findings

Of the 1,443 dogs examined, 230 (15.9%) were seropositive in at least one ELISA, whereas PCR-RFLP revealed that 356 animals (24.7%) were positive for L. infantum DNA. Results indicated that the associated factors with infection were family income<twice the Brazilian minimum salary (OR 2.3; 95%CI 1.4–3.8), knowledge of the owner regarding the vector (OR 1.9; 95%CI 1.1–3.4), the dog staying predominantly in the backyard (OR 2.2; 95%CI 1.1–4.1), and a lack of previous serological examination for VL (OR 1.5; 95%CI 1.1–2.3).

Conclusions

PCR detected a high prevalence of L. infantum infection in dogs in an area under the Control Program of VL intervention. Socioeconomic variables, dog behavior and the knowledge of the owner regarding the vector were factors associated with canine visceral leishmaniasis (CVL). The absence of previous serological examination conducted by the control program was also associated with L. infantum infection. It is necessary to identify the risk factors associated with CVL to understand the expansion and urbanization of VL.

Visceral leishmaniasis (VL) is a disease caused by the parasite Leishmania infantum, and dogs are the most important domestic reservoirs of the agent. During recent decades, VL has expanded to large Brazilian urban centers. In the present work, we have demonstrated by using molecular techniques that the rate of canine infection as detected by serology has been considerably underestimated. Two groups of seronegative dogs (infected and non-infected according to molecular methods) were further evaluated from data obtained through interviews with owners of the animals. The factors associated with Leishmania infection in dogs were a family income of less than two minimum salaries, the knowledge of the owner regarding the vector, the dog spending most of its time in the backyard and the dog never having had a previous serological examination. Awareness regarding the factors associated with canine infection will improve health services and the understanding of the disease's expansion in urban areas.

Application of an improved enzyme-linked immunosorbent assay method for serological diagnosis of canine leishmaniasis

Accurate diagnosis of canine leishmaniasis (CanL) is essential toward a more efficient control of this zoonosis, but it remains problematic due to the high incidence of asymptomatic infections. In this study, we present data on the development of enzyme-linked immunosorbent assay (ELISA)-based techniques for the detection of antibodies against the recombinant protein Leishmania infantum cytosolic tryparedoxin peroxidase (LicTXNPx) and a comparison of the results with those employing soluble Leishmania antigens from promastigote or amastigote forms and the homologue recombinant protein L. infantum mitochondrial TXNPx (LimTXNPx). Moreover, we offer an evaluation of the diagnostic potential of rK39 for CanL in the Portuguese canine population and propose an improvement to the existing ELISA-based serological techniques by combining the LicTXNPx and rK39 antigens as a Leishmania antigen mixture (LAM). The data demonstrated that ELISAs based on soluble promastigote or amastigote antigens had generally higher levels of sensitivity for detection of antibodies in symptomatic or asymptomatic dogs than for detection of those against isolated recombinant proteins. Nevertheless, the specificities were found to be similar for all target antigens used. Importantly, the LAM-ELISA methodology improved the overall sensitivity, maintaining a high overall level of specificity. In addition, it was demonstrated that the detection of anti-LAM IgG2 can increase the accuracy of the serological diagnosis. Overall, the obtained results showed that the strategy of combining two well-defined Leishmania antigens, LicTXNPx and rK39, proved to be a sensitive and specific improvement to current serological diagnosis of CanL, being a useful tool for the detection of both clinical and subclinical forms of canine Leishmania infection.

Transmission, reservoir hosts and control of zoonotic visceral leishmaniasis

Zoonotic visceral leishmaniasis (ZVL) caused by Leishmania infantum is an important disease of humans and dogs. Here we review aspects of the transmission and control of ZVL. Whilst there is clear evidence that ZVL is maintained by sandfly transmission, transmission may also occur by non-sandfly routes, such as congenital and sexual transmission. Dogs are the only confirmed primary reservoir of infection. Meta-analysis of dog studies confirms that infectiousness is higher in symptomatic infection; infectiousness is also higher in European than South American studies. A high prevalence of infection has been reported from an increasing number of domestic and wild mammals; updated host ranges are provided. The crab-eating fox Cerdocyon thous, opossums Didelphis spp., domestic cat Felis cattus, black rat Rattus rattus and humans can infect sandflies, but confirmation of these hosts as primary or secondary reservoirs requires further xenodiagnosis studies at the population level. Thus the putative sylvatic reservoir(s) of ZVL remains unknown. Review of intervention studies examining the effectiveness of current control methods highlights the lack of randomized controlled trials of both dog culling and residual insecticide spraying. Topical insecticides (deltamethrin-impregnated collars and pour-ons) have been shown to provide a high level of individual protection to treated dogs, but further community-level studies are needed.

Forum: geographic spread and urbanization of visceral leishmaniasis in Brazil. Introduction

The geographic spread and urbanization of visceral leishmaniasis in Brazil has been described since the early 1980s. However, the putative factors associated with this process, its full characterization, and the implications for disease control still challenge researchers and Public Health professionals. Although the available data show that the disease occurs mainly in urban areas, current knowledge is insufficient to claim specificity in urban transmission as compared to rural niches. Transmission scenarios in urban settings appear to be highly heterogeneous, each showing some degree of similarity to the rural epidemiological pattern. The understanding of a relatively recent and complex problem like the introduction, spread, and maintenance of visceral leishmaniasis in urban areas requires new analytical approaches that consider the network of relevant variables and more elaborate methods capable of capturing the dynamics of the environmental and demographic transformations taking place in transmission areas.